Business Combinations - Narrative (Details) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2021 USD ($) business_combination	Dec. 31, 2021 USD ($)
Business Acquisition [Line Items]
Number of business combinations | business_combination		1
Acquisition costs			$ 34
Purchase price			$ 176
Business combination goodwill is deductible for income tax purposes			100.00%
Prepaid expenses and other assets		$ 58	$ 58
Magellan Complete Care
Business Acquisition [Line Items]
Purchase price	$ 1,037	$ 28
Outstanding equity interests	100.00%
Receivables			7
Payable			27
Amounts due government agencies			18
Goodwill, Purchase Accounting Adjustments			$ 10